Optical drives capable of recording data on optical media are well known in the art. These drives include the Compact Disc-Read/Write (CD-R) drives, which can read CD-based formats and read and write to Write Once Media, and Compact Disc-Rewritable (CD-RW) drives, which can read CD-based formats and read and write to Write Once Media and Rewritable Media. The standard CD recordable and rewritable media and format is set forth in what is commonly referred to in the art as the “orange book”. Under the standard, the writing of data is described in terms of “T”, where T is a fundamental unit of time, and has a minimum mark of 3T and a maximum mark of 11T. The writing of the 3T mark is the most critical due to its size, thus the standard sets forth when to heat and cool the recording material in writing the 3T mark. A Non-Return to Zero Inverted (NRZI) method of recording is used, where a zero is represented by a change in the write control signal and a one by no change. When the write control signal first changes, the heating of the media begins. When the write control signal is changed again, the heating ends, and the media is cooled to end the mark. When the media is heated and cooled to form a 3T mark varies with the type of media, and is set by the standard.
Prior to the writing of data, the writing profile for the particular recording media need to be calibrated to ensure that the data may be reliably read. For this purpose, each CD-R or CD-RW has an area called the “calibration area”, where marks are made and sampled to determine the quality of the writing. Analog signals carrying the sampled marks are converted to digital signals by an analog-to-digital converter (ADC). The digital signals contain process amplitude and reflection values of the sampled marks, which are then used to compute the beta and gamma values according to the orange book. Beta and gamma values are well known in the art and will not be further described here. In this specification, the beta and gamma values are collectively referred to as “calibration values”. The calibration values are then compared to reference values to determine the quality of the sampled marks. Based upon the result, the write control parameters may be adjusted.
In conventional CD-R or CD-RW controllers, a subsystem separate from the servo subsystem is required to sample the marks. This is so that the servo may maintain its position over the recording media while the sample is collected. However, the need for the separate subsystem increases the cost of manufacturing the controller. It also increases the amount of components which increases the risk of component failure.
Accordingly, there exists a need for an improved method and system for calibration of writing to an optical media. The improved method and system should decrease the cost of manufacturing the controller and decrease the risk of component failure. The present invention addresses such a need.